Hi,

First of all don’t panic (yet). An email change can be performed by either the root user (better hope is not the case if not intended) or by aws support. If that is not intended and aws support allowed that, then you should immediately get in touch with the accounts admin and get in contact with AWS support.

If the account was yours or of your company, make sure the admin is still able to do manage the account and start remediation actions as described in this article: https://aws.amazon.com/premiumsupport/knowledge-center/potential-account-compromise/